Vanilla is highly prized for use in flavoring a broad array of foodstuffs. Its use is restricted by high costs stemming from the complex, low yielding methods associated with its manufacture. Vanillin having the structure: ##STR1## is one of the principal components responsible for the characteristic aroma and flavor of vanilla extract. Several processes for producing vanillin in combination with other materials which have boiling points close to that of vanillin are known, for example:
Labuda, et al, I, U.S. Letters Pat. No. 5,128,253 issued on Jul. 7, 1992; Title: "BIOCONVERSION PROCESS FOR THE PRODUCTION OF VANILLIN"; PA1 Labuda, et al, II, U.S. Letters Pat. No. 5,279,950 issued on Jan. 18, 1994; Title: "BIOCONVERSION PROCESS FOR THE PRODUCTION OF VANILLIN"; and PA1 Dolfini, et al, U.S. Letters Pat. No. 4,927,805 issued on May 22, 1990; Title: "HYDROLYSIS OF CURCUMIN". PA1 (1) distilling a mixture of vanillin and said second organic chemical in the presence of an azeotrope forming agent which is dibenzyl ether having the structure: ##STR13## (2) recovering a single phase liquid mixture of vanillin and dibenzyl ether azeotroping agent as overhead product and said second organic chemical from the still pot (for example, parahydroxybenzaldehyde having the structure: ##STR14## (3) separating said vanillin from said dibenzyl ether azeotrope forming agent by cooling said single phase mixture of vanillin and dibenzyl ether whereby vanillin crystals precipitate from said mixture of vanillin and dibenzyl ether; and PA1 (4) separating said vanillin crystals from said single phase mixture of vanillin and dibenzyl ether. PA1 (2) Since dibenzyl is an azeotroping co-distillate, the pot temperature during distillation remains relatively low: less than 170.degree. C. at 7-8 mmHg throughout the distillation versus 210.degree. C. or higher if a batch distillation is attempted to be carried out using vegetable oil as a still base or 190.degree.-210.degree. C. if other azeotroping agents (also newly discovered) are attempted to be used (FIGS. 3 and 4 described, infra, show that phenyl benzoate and vanillin form a maximum boiling azeotrope and FIG. 4 described, infra, illustrates likewise the formation of a maximum boiling azeotrope for phenyl ethyl benzoate) as co-distillates; PA1 (3) Although dibenzyl ether azeotropes with such by-products resulting from forming vanillin as p-hydroxybenzaldehyde (pHB), significant differences between the azeotrope temperatures allow separation of such materials as parahydroxybenzaldehyde from the vanillin; PA1 (4) Using dibenzyl ether as the azeotroping agent, continuous distillations are conveniently carried out. Thus, for example, with an average composition of 88% vanillin and 12% parahydroxybenzaldehyde, one can predict that the respective distillate composition would be 98.5:1.5 and the bottoms would be 65:35 (vanillin:parahydroxybenzaldehyde) for a single pass through a 10-plate column. Recycling allows recovery of most of the vanillin; PA1 (5) As a co-distillate, dibenzyl ether prevents vanillin from subliming. Sublimation is problematical because the redeposited crystals plug distillate and vacuum lines and other equipment; PA1 (6) As a co-condensate, dibenzyl ether solvolizes the vanillin thereby minimizing line blockage; and PA1 (7) Vanillin is minimally soluble at cold temperatures in dibenzyl ether and dibenzyl ether is a liquid to 1.degree. C.; thus we have been able to determine that vanillin readily crystallizes from dibenzyl ether: PA1 Holmes, et al, INDUSTRIAL AND ENGINEERING CHEMISTRY, Volume 62 (1) January 1970, pages 21-31; PA1 Orye, et al, INDUSTRIAL AND ENGINEERING CHEMISTRY, Volume 57 (5) May 1965, pages 18-26; and PA1 Wilson, Journal of the American Chemical Society, Volume 86, pages 127-130.
Thus, many of these processes produce vanillin in combination with such materials as parahydroxybenzaldehyde having the structure: ##STR2##
Vanillin, a solid with a melting point of 82.degree. C., is a valuable ingredient. However, it is a difficult compound to distill from such mixtures. Not only is it a high boiling substance subject to decomposition, but it is also limited by the need to keep it liquid. This requires a relatively high (&gt;1 mmHg) pressure and thus, temperature at which it must be distilled is high. The distillation is further complicated by its propensity to sublime. Distillation and vapor and vacuum lines are constantly subject to being clogged by the deposition of sublimed vanillin. Because of the relatively high temperatures at which vanillin has to be distilled, pot decomposition becomes a twofold problem.
Decomposition makes it difficult to maintain low pressure which leads to higher pot temperatures which, in turn, lead to even more decomposition. During the distillation procedure, the pot temperature typically starts out at 180.degree. C. at 1-5 mmHg pressure when the vanillin begins to distill and the pot temperature rises to 220.degree. C. or higher towards the end of the distillation with the pressure difficult to maintain below 20 mmHg.
Decomposition leads to polymerization and solidification of the pot contents. This makes it impossible to carry out commercial-size pot distillations (or "batch") distillations. Batch distillations run as such can only be accomplished in small (22 liter) glass stills which require strong caustic soap digestion with direct steam injection needed to clean the apparatus adequately. Glass pots can only be subjected to this procedure a few times before they fail in operation. Such decomposition also leads to off-odors and yellow color in the resulting vanillin product. Previously, intensive crystallization is required by practitioners in the art to reduce such off-odors and yellow color.
When vanillin is produced in combination with such materials as parahydroxybenzaldehyde, practitioners in the art have previously relied on multiple crystallization of vanillin to reduce the parahydroxybenzaldehyde and other chemicals to levels generally as low as 1% or even less. This leads to significant loss of the valuable vanillin.
Some of the aforesaid decomposition of the vanillin has been found by practitioners in the art to be avoided by utilizing thin-film evaporation to minimize the exposure to heat. However, this approach also has its attendant problems. A relatively non-volatile solvent is required and the sublimation as discussed, supra, gives rise to problems. Thus, with the running of a short path, wiped film evaporator, distillation capacity is limited by the high condenser temperatures since the vapor needed for condensation of vanillin as a liquid and sublimation lead to system breakdown fairly regularly. Additionally, any cold spots in the distillation lines lead to occasional line "freeze ups" which become difficult to isolate and remove.
Thus, we have discovered that the ideal co-distillate is to be a liquid at low temperature and reduces the temperature at which the vanillin can be distilled. The liquid co-distillate will thus act as a solvent for the vanillin to keep it from subliming and freezing out.
The thus-discovered co-distillate is dibenzyl ether having the structure: ##STR3##
Prior art techniques have been developed for separation of co-reaction products from vanillin including separation of aldehydes from vanillin including Chemical Abstracts, Volume 107:108522p, Cela, et al, abstract of Anal. Chim. Acta 1986, Volume 191, pages 283-297 where a theoretical model is described for quick pre-optimization of binary multistep gradient elutions in liquid chromatography including separation of vanillin from various benzaldehyde derivatives.
In Chemical Abstracts, Volume 100:101716b, an azeotropic method for determination of weight loss and determination of moisture and content of vanillin and parahydroxybenzaldehyde in vanilla beans is disclosed.
Although mixtures of vanillin and dibenzyl ether along with many other materials are known, for example, Buil, et al, parfums, cosmetiques, aromes, No. 52, August-September 1983, pages 45-49, at page 46, nothing in the prior art shows mixtures consisting of vanillin and dibenzyl ether and thus, nothing in the prior art shows the use of dibenzyl ether as an azeotroping agent for separation of vanilla from other organic chemicals produced therewith, for example, Parahydroxybenzaldehyde.
Azeotropic distillations and data using as one of the components an organic ether are known in the literature. Thus, Horsley, et al, "AZEOTROPIC DATA", published June 1952 by the AMERICAN CHEMICAL SOCIETY ("Advances in Chemistry Series") discloses a binary azeotrope formulation containing benzyl phenyl ether having the structure: ##STR4## an .alpha.-toluic acid having the structure: ##STR5## at page 218 and further discloses benzyl ether having the structure: ##STR6## in combination with phenyl benzoate having the structure: ##STR7## at page 249 (No. 14500) (as a "nonazeotrope"); and further discloses the combination of isoamyl salicylate having the structure: ##STR8## in combination with benzyl phenyl ether having the structure: ##STR9## (No. 14493) (also indicated as a nonazeotrope). Such disclosure is considered to teach away from our invention.
Berg, I, U.S. Letters Pat. No. 5,382,329 issued on Jan. 17, 1995 discloses the separation of 1-decene from decane by azeotropic distillation using, inter alia, methyl, t-butyl ether as the azeotroping agent. Berg, II, U.S. Letters Pat. No. 5,382,330 issued on Jan. 17, 1995 discloses the separation of 1-octene from octane by azeotropic distillation using, inter alia, t-amyl methyl ether as the azeotroping agent.
Berg, III, U.S. Letters Pat. No. 5,401,366 issued on Mar. 28, 1995 discloses the separation of 1-butanol from 2-pentanol by means of extractive distillation using, inter alia, butyl ether as the "extractive" agent.
Nothing in the prior art including the aforementioned references implicitly or explicitly discloses our invention covering mixtures consisting of dibenzyl ether and vanillin and methods of separating vanillin from second organic chemicals produced therewith such as parahydroxybenzaldehyde using dibenzyl ether as an azeotroping agent. Furthermore, nothing in the prior art discloses the products produced by such methods.